Effect of suppression of FSH with a GnRH antagonist (acyline) before and during follicle deviation in the mare.
A GnRH antagonist (Acyline) was used to study the role of FSH in early development of a follicular wave in 61 mares. In Experiment 1, a single dose of 3 mg per mare, compared with 0 and 1 mg, suppressed both the FSH and follicle responses to exogenous GnRH. In Experiment 2, high concentrations of FSH were induced by two successive ablations of all follicles >/= 6 mm on days 10 and 13 (day 0 = ovulation). A single treatment with Acyline resulted in significantly greater suppression of plasma concentrations of FSH than a single treatment with charcoal-extracted follicular fluid (source of inhibin) or oestradiol. Suppression of FSH was not significantly different between the group treated with Acyline alone and a group treated with a combination of Acyline, inhibin and oestradiol. In Experiment 3, all follicles were ablated on day 10 to induce an FSH surge and a new follicular wave. Acyline treatment on day 10 resulted in an immediate decrease in FSH, without a significant effect on day of emergence of a new wave or growth of follicles from 7 to 11 mm on days 11-13. Treatment on day 15, a day before expected follicle deviation and after the peak of the wave-stimulating FSH surge, resulted in an immediate decrease in FSH and cessation of follicle growth. Results indicated that growth of follicles for about 2 days after wave emergence was independent of FSH. In contrast, during the decline in the wave-stimulating FSH surge and before follicle deviation, growth of follicles was dependent on FSH.
Checura
C M
CM
Eutheria Foundation, Cross Plains, WI 53528, USA.
Beg
M A
MA
Gastal
E L
EL
Gastal
M O
MO
Wiltbank
M C
MC
Parrish
J J
JJ
Ginther
O J
OJ
D000818:Animals; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D005640:Follicle Stimulating Hormone / Q000037:antagonists & inhibitors / Q000097:blood / Q000502:physiology*; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage / Q000037:antagonists & inhibitors*; D006736:Horses / Q000502:physiology*; D007265:Inhibins / Q000494:pharmacology; D009842:Oligopeptides / Q000494:pharmacology*; D006080:Ovarian Follicle / Q000033:anatomy & histology / Q000187:drug effects / Q000502:physiology*; D010053:Ovary / Q000000981:diagnostic imaging; D014463:Ultrasonography
D009842:Oligopeptides; D007987:Gonadotropin-Releasing Hormone; D004958:Estradiol; D007265:Inhibins; D005640:Follicle Stimulating Hormone; C109238:acyline